1. Field of the Invention
The present invention relates to an engine including a crankshaft rotatably supported by a crankcase, an oil pan connected to a lower portion of the crankcase, and an oil pump interlocked for rotation with the crankshaft. In particular, the present invention relates to an improved oil pump mounting structure for the engine.
2. Description of Background Art
Conventionally, a pump housing for an oil pump has been removably mounted on a lower portion of a crankcase. A pump housing of this type has been disclosed, for example, in Japanese Patent Publication No. Sho 62-34950.
The above-described configuration includes the pump housing removably mounted on a lower portion of the crankcase. However, this configuration has problems since the position of the oil pump is raised, the center of gravity of the engine is raised, the pumping loss of the oil pump is increased, the maintenance is degraded, and an oil passage is complicated.
In view of the foregoing, the present invention has been made, and an object of the present invention is to provide an oil pump mounting structure for an engine, which is capable of making the center of gravity of the engine relatively low. The present invention also has as its object to improve the suction efficiency and the maintenance of the oil pump.
To achieve the above object, according to a first aspect of the present invention, an oil pump mounting structure for an engine includes a crankcase rotatably supporting a crankshaft, an oil pan connected to a lower portion of the crankcase, and an oil pump interlocked for rotation with the crankshaft. The pump housing of the oil pump is removably mounted on a mounting portion provided on the bottom of the oil pan.
With this configuration, it is possible to set the oil pump at a relatively low position. Accordingly, the center of gravity of the engine can be lowered and the suction efficiency and the maintenance performance of the oil pump can be improved.
According to a second aspect of the present invention, in addition to the configuration of the first aspect of the present invention, an oil strainer is connected to an inlet of the oil pump and is fixedly held between the oil pan and the pump housing. With this configuration, it is possible to fix the oil strainer between the oil pan and the pump housing without use of specialized parts for fixture such as bolts. Accordingly, and the number of parts and the number of assembling steps can be reduced. Furthermore, since an oil suction passage between the inlet of the oil pump and the oil strainer can be shortened, the pumping loss of the oil pump can be reduced.
According to a third aspect of the present invention, in addition to the configurations of the first and second aspects of the present invention, a relief valve is connected to an outlet of the oil pump and is fixedly connected between the oil pan and the pump housing in a direction parallel to the direction where the oil strainer is held. Furthermore, an oil filter is connected to the outlet and is mounted to an outer surface of a side wall of the oil pan. With this configuration, the oil strainer is held between the pump housing and the oil pan. Accordingly, the relief valve can be disposed by making effective use of a space formed on a side of the oil strainer. Also, the relief valve is directly connected to the pump housing of the oil pump. Accordingly, it is possible to shorten and simplify an oil discharge passage from the oil pump to the oil filter. In addition, a relief port of the relief valve can be easily set in oil in the oil pan. Accordingly, it is possible to prevent the oil from bubbling.
According to fourth aspect of the present invention, in addition to the configurations of the first through third aspects of the present invention, a partition wall is provided in the pump housing so that a power transmission chamber partitioned from an oil reservoir chamber formed in the oil pan is formed between the partition wall and a side wall of the oil pan. Furthermore, a rotating member is rotatable by power transmission from the crankshaft and is fixed to an end portion on the power transmission chamber side of a drive shaft rotatably supported by the pump housing. With this configuration, the rotating member, which is rotated for transmitting power from the crankshaft to the drive shaft of the oil pump, does not agitate the oil reserved in the oil reservoir chamber in the oil pan. Accordingly, it is possible to prevent the occurrence of friction loss and oil mist due to agitation of the oil.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.